Original subtitles

Our world is not always the same.

Hidden from our view lies a different world...

..creatures utterly unlike us...

..almost alien...

..yet they are more numerous than any other group on the planet.

Welcome to the fascinating world of the arthropods - spiders,

scorpions and insects.

Today, we have new camera techniques that will allow us

to reveal in greater detail than ever before their lives -

the way they fight and feed and reproduce.

This series uses specially developed 3-D camera technology

to study the micro world in extraordinary detail,

both on location and in specially constructed environments.

We'll witness the births, the challenges they face

and the moments when their lives hang in the balance.

And that may help us understand how it is that today

over 80% of all animal species on this planet are arthropods.

In the series,

we'll see the way they have evolved from the comparative

simplicity of the millipede to vast colonies that contain

hundreds, even millions, of individuals.

We'll witness the most extraordinary transformations

in the animal kingdom.

We'll meet ants that farm,

spiders that can cast their webs...

..and the bug that wears the bodies of its victims as a disguise.

Welcome to a strange and dangerous world.

Ever since they first appeared on land, the arthropods have

been fighting one another - for territory, a mate and a meal.

To survive, every living thing must eat

and around 10% of arthropods eat other arthropods.

Some of the most remarkable hunting strategies in the animal kingdom

are happening right under our noses.

These are whirligig beetles and they live on ponds throughout the world.

They use the water's surface very like radar to detect their prey.

A stick insect held fast to the water by surface tension.

Its struggles send vibrations across the water's surface.

The whirligig senses them and puts its water radar into action.

It spins at a rate of around 12 times a second.

This spinning motion sends tiny ripples across the water.

These bounce back from the stick insect.

The whirligig detects the faint echoes in much the same way as radar

and it closes in on the victim.

Whirligigs all over the pond join in.

They too have their own water radar.

The stick insect stands little chance against this voracious horde.

Whirligigs use the environment to help them

detect the presence of prey...

..but the surface of water

is not the only media for carrying messages.

Some predators have developed more sophisticated ways of hunting.

One group of arthropods, the spiders,

produce a substance so versatile and so strong

it's used by 30,000 different species - silk.

They use it for a multitude of different purposes -

for transport, for spinning a filament that

catches in the wind and then carries them aloft, as trap lines,

as lining for their nests, but, above all,

they use it to trap their prey.

These striking patterns of silk are made by one of the rainforest's

most effective predators - Argiope, the St Andrew's Cross spider.

Nobody is sure why Argiope constructs this conspicuous

white silken cross at the centre of her web.

Some experts think that it serves as a warning,

but this fly certainly didn't notice it.

Argiope wraps her catch to prevent it from escaping,

using not web silk, but a different non-stretch kind...

and then she paralyses it with her toxic venom.

She'll eat it later.

Soon, another potential victim strays onto the web -

a Portia spider.

But before Argiope can strike,

Portia retreats to the edge of the web.

And then she does something very curious.

She plucks on very carefully chosen strands.

She creates rhythmic vibrations that calm Argiope.

Instead of attacking Portia, Argiope returns to the centre of her web...

..and that is exactly where Portia wants her...

..because Portia hunts other spiders

and has Argiope in her sights.

She moves off the web, so that she can survey the scene.

Over many hours, she moves around the surrounding

branches in search of the best point to launch an attack.

She uses these robotic movements to camouflage herself from Argiope.

To poorly sighted creatures, she probably looks like a thread

fluttering in the wind and this buys time for her surveillance.

Portia has superb eyesight and she can judge angles and distances

with great precision.

She's planning to pounce on Argiope.

She has to be exactly on target.

Her venom kills Argiope instantly.

Like most spiders, she can't eat solid food, so she pumps

her digestive juices into her prey and then sucks the corpse dry.

Our planet is home to over a million species of arthropods.

Today, they outnumber other animal species four to one.

That's part of their fascination - their variety.

And that variety is evident in the predators,

the bugs that hunt other bugs...

..and the most ingenious of all are the spiders.

Most spiders capture their prey in a web.

Glue on the silken filaments traps a victim

and vibrations through them tell the spider that a meal is waiting.

But webs come in many shapes and forms and different spiders

have favoured different places in which to construct them.

The inside of a log is a good place to catch beetles

and even small reptiles.

This tangle of silk is the home

of one of Australia's most feared spiders -

the highly venomous redback.

Despite its appearance, this web is actually highly complex

and very finely engineered.

It contains some of the strongest silk produced by any spider...

..so strong than she can catch

and transport prey far larger than herself.

First, she winds strands of silk around the struggling beetle

to immobilise it.

When the beetle tires, she bites.

She must pull her victim up to the part of the web where she lives.

She starts snipping and re-attaching the lines of silk.

These lines are under tension, they're spring-loaded,

and that allows the redback to haul huge weights around her web.

The tiny male watches as she retrieves her catch.

Spider silk is as stretchy as elastic,

but harder to snap than steel.

As day turns to night and the forest plunges into darkness,

nocturnal predators are coming out to hunt.

One of them is Deinopis - the ogre-faced spider.

She is found throughout the tropics

and she uses silk in a very different way.

She has turned it into a net.

Her sticklike body makes her hard to spot amongst the branches.

Her huge central pair of eyes are 2,000 times more sensitive

than ours.

And to keep it that way, she completely rebuilds her retina

at the back of each eye every single day.

They enable her to hunt in almost complete darkness.

She hangs an inch or so above the forest floor

from a series of silk lines.

She strikes.

She stretches her net over her prey...

..and then wraps it in silk to immobilise it.

At last, she begins a slow process of digesting her meal.

For her prey, at least, the end is quick.

Her fast-acting venom kills almost instantly.

But venom can have other uses and some victims are not so lucky.

Venom can be used for both defence and attack,

but some arthropods use it in a more subtle way.

Not to kill, but to control.

In the woodlands of Africa and South Asia,

lives a creature that has mastered the use of venom like few others.

Meet the jewelled cockroach wasp.

Her iridescent body stands out brightly against the forest floor,

though the purpose of her bright colouration is not known.

Certainly, any bug that does spot her will do well to steer clear.

She hunts, but not for herself.

This cockroach is exactly what she's been looking for.

It's much larger and stronger than she is.

Nevertheless, she attacks.

She won't kill it. She wants it alive.

First, she injects it with a venom that paralyses its front legs.

This prevents it fighting her off.

Now she injects a second venom directly into its brain.

Amazingly, this instantly stops the cockroach responding to danger.

It becomes completely docile.

She leads her victim to an underground burrow.

Here, she'll lay her eggs directly onto the cockroach's body.

She conceals the burrow's entrance with leaf litter.

This will stop other predators finding the cockroach or her lava.

The lava spends five days sucking the cockroach's body fluids,

then it will burrow inside and begin to feed.

It eats the least essential parts first

and saves the nervous system and the breathing system for last.

A process that takes ten days or more.

And for all that time the cockroach is alive and powerless to respond.

Over a period of weeks, the lava continues to grow and develop

until, eventually, all that remains of the cockroach

is a dead, empty husk.

And from it emerges a fully mature adult wasp...

..ready to repeat the gruesome cycle for itself.

We have seen some of the deadly ways in which arthropods

prey upon one another.

The way these creatures hunt has shaped their bodies and their lives.

The struggle for survival amongst arthropods is often brutal,

but that's a key to their success.

The strongest survive to produce the next generation.

In the next programme, I'll be looking at how the desire for sex

has shaped bugs into a bewildering array of forms.

We'll see how courtship is not always what it seems.

Some males bribe females into having sex.

And others trick them.

And we'll see the next generation of micro-monsters take their first

tentative steps into their small and often dangerous world.